Field of the Invention
The present invention relates to an impact dot print head included in a printer and more particularly to an impact dot print head wherein an armature which is disposed so as to be pivotable about a pivot shaft and between a printing position and a stand-by position is actuated with a magnetic flux which is generated by energizing a coil wound round a core opposed to the armature, to effect printing, as well as a printer using the impact dot print head.
Heretofore there has been known an impact dot print head wherein an armature with a printing wire connected thereto is pivoted between a printing position and a stand-by position, and when the armature is pivoted to the printing position, a tip of the wire is brought into collision with recording paper to effect printing.
In a certain impact print head of this type, a magnetic circuit is formed around the armature to be pivoted, the magnetic circuit causing the armature to be attracted from a stand-by position to a printing position with a magnetic flux generated by a coil to effect printing.
For example, the magnetic circuit comprises a yoke having a core with a coil wound thereon to generate a magnetic flux, an armature spacer disposed near an armature at a position in contact with the yoke and not obstructing a pivotal motion of the armature, and the armature.
On an inner periphery side of the coil the magnetic flux generated by the coil flows from the core in one direction toward the armature, but at a position offset from the inner periphery side of the coil the magnetic flux tends to diffuse outwards. Consequently, this outwardly diffusing magnetic flux portion sometimes flows from the core to the armature spacer directly without through the armature. Once there occurs such a magnetic flux as flows from the core directly to the armature spacer without flowing through the armature, i.e., so-called leakage flux, the attractive force acting to attract the armature to the core is diminished.
Recently, various countermeasures have been taken to increase the printing speed and printing pressure, but due to a decrease of the attracting force caused by the generation of the aforementioned leakage flux it is difficult to fully attain the speed-up of printing speed and an increase of the printing pressure.
Accordingly, it is an object of the present invention to prevent an armature attracting force for a core from being decreased by the generation of leakage flux.
It is another object of the present invention to increase the printing speed and printing pressure.
The above objects of the present invention are achieved by novel an impact print head and a printer including the same according to the present invention.
In one aspect of the present invention there is used an armature spacer having side yoke portions, the side yoke portions each extending in a direction away from a core and confronting an armature, thereby suppressing a direct flow of a coil-generated magnetic flux from the core to the armature spacer without through the armature and allowing the coil-generated magnetic flux to flow from the core to the armature spacer through the armature, to form a satisfactory magnetic circuit from a core of a yoke up to the yoke successively through the armature and the armature spacer and thereby preventing an armature attracting force for the core from being decreased by the generation of leakage flux.
In another aspect of the present invention there is used an armature spacer having side yoke portions, the side yoke portions each extending in a direction away from a core and confronting an armature, thereby suppressing a direct flow of a coil-generated magnetic flux from the core to the armature spacer without through the armature and allowing the coil-generated magnetic flux to flow from the core to the armature spacer through the armature, to form a satisfactory magnetic circuit from a core of a yoke up to the yoke successively through the armature and the armature spacer, thereby preventing an armature attracting force for the core from being decreased by the generation of leakage flux, to increase the printing speed and printing pressure.